1. Technical Field
The present invention relates to a supercapacitor and, more particularly, to a supercapacitor having increased energy density through aluminum ions and to the use thereof.
2. Description of the Related Art
Typically, a supercapacitor is referred to as an electrical double-layer capacitor (EDLC) or an ultra-capacitor, and is an energy storage device using a charge phenomenon through a surface chemical reaction or through simple ion transport and adsorption to the electrode and electrolyte interfaces, unlike batteries, which use chemical reactions.
Specifically, a supercapacitor is configured to include electrodes attached to current conductors and an electrolyte solution incorporated thereto, and a pair of charge layers (an electrical double layer) having different signs on electrode interfaces. Such a supercapacitor enables rapid charge and discharge, exhibits high charge and discharge efficiency, and obviates a maintenance due to very low degradation even upon repetition of charge-discharge cycles, thereby resulting in a semi-permanent cycle life. Hence, a supercapacitor is receiving attention as a next-generation energy storage device useful as a replacement for batteries or supplementary batteries.
Such a supercapacitor is advantageous because of rapid charge and discharge, longer cycle life than that of secondary batteries, and a wide operating temperature range. However, it suffers from very low energy density compared to secondary batteries. With the goal of solving this problem, a supercapacitor is provided in various forms, and techniques for increasing energy density by performing both intercalation and deintercalation of lithium ions at either electrode have recently been developed. However, such a supercapacitor, called a lithium ion capacitor, is low in price competitiveness because lithium is expensive and it is difficult to form the electrode that enables the intercalation and deintercalation of lithium ions, thus making it difficult to achieve actual application thereof. In a similar form, a lead oxide capacitor has been developed using lead oxide, the price of which is lower than that of lithium, but its actual application is also difficult, owing to the use of lead, which is a poisonous material.